This invention relates to controllers for automotive engines, and more particularly to engine controllers with improved restarting performance.
In recent automotive engines, fuel injectors have replaced the carburetor. When fuel injectors are used as the fuel supply device of automotive engines, the amount of air intake into the engine is measured and an amount of fuel corresponding to the amount of air is injected from the fuel injectors. The amount of injected fuel can be adjusted in accordance with the operating condition of the engine. Thus, the fuel injectors are capable of performing strict control of the fuel supply necessary to satisfy the demand for the ever higher performance level of the engine, or to satisfy the strict regulations enforced against the polluting exhaust gas contents. To meet the demands for better performance, an increasing number of functions must now be provided by the engine controller. Thus, it is necessary that the engine controllers provide control not only of the injectors themselves, but also of the fuel pump for supplying the fuel to the injectors and of the radiator fan for cooling the engine.
To improve restarting performance, in particular, Japanese Patent Publication (Kokoku) No. 63-38537 proposes to augment the fuel pressure at the restart of the engine if the temperature of the engine is high. This Japanese patent publication controls the engine as follows.
First, it is judged whether or not the temperature of the engine is above a predetermined reference level at the restart of the engine. If the temperature of the engine is high, further judgment is made as to whether or not the time elapsed after the engine was stopped is within a predetermined length. If the judgement is affirmative (i.e., if the temperature of the engine is high and the time after the engine was stopped is within a predetermined length), the fuel pressure is increased to augment the amount of fuel and the idling RPM.
The control method proposed by the above Japanese Patent Publication improves the restarting performance. However, the method may be insufficient under certain conditions. For example, if the engine is stopped when the ambient temperature is high or after the vehicle has been driven for a long time at a high speed, the temperature of the engine remains high for a prolonged period. The temperature of the engine and of the parts associated therewith may even rise after the engine is stopped, since the engine is no longer cooled by the wind generated by the running vehicle. Thus, the temperature of the injectors and of the fuel within them may rise.
If the engine is restarted at the time when the injectors and the fuel within them are still at a high temperature, the vapor generated within the injectors hinders the supply of fuel. It thus becomes impossible to supply an appropriate amount of fuel corresponding to the amount of intake air. The augmentation of the amount of fuel becomes impossible. Since the necessary amount of fuel cannot be supplied, the proper air/fuel ratio cannot be maintained. The rotation of the engine thus becomes unstable, and the engine may even stall.